I understand that there are no flights for a couple of months. When I went overland KTM - Lhasa at the beginning of this year, there were several others who went back in the empty landcruisers that took us to Lhasa.

A good guesthouse in Lhasa is the Pentoc Guesthouse. A single room is $US5. You'll be able to organise your journey to Nepal from there.

I flew Bangalore to Delhi, then onto Kathmandu. After this, it was overland to Lhasa, Tibet. I was going further into China, so I flew from Lhasa to Chengdu, then down to Kunming, before going up to Beijing.

Whilst in Nepal, I caught a bus from Kathmandu to Pokhara and down to Lumbini, which is very close to the Indian border. You could consider this route back to Delhi